Legal Considerations for WHO’s ‘Possibly Carcinogenic’ Aspartame Classification

July 20, 2023

On July 14, 2023, the World Health Organization (WHO) published a summary of two findings regarding aspartame, an artificial sweetener found in many consumer products. One finding categorized aspartame as “possibly carcinogenic,” which potentially increases businesses’ litigation risk and regulatory scrutiny regarding aspartame-containing products, while the other finding reaffirmed that the current acceptable daily intake of aspartame should remain the same, noting that significant limitations existed for the new classification. Going forward, businesses that sell aspartame-containing products may need to address any fallout from the WHO’s findings.

The two findings were published by WHO research subgroups International Agency for Research on Cancer (IARC) and Joint FAO/WHO Expert Committee on Food Additives (JECFA). The US Food and Drug Administration (FDA) then rejected the WHO’s classification of aspartame as “possibly carcinogenic.”

WHO Classifies Aspartame as ‘Possibly Carcinogenic’ in IARC Finding

IARC is the WHO’s main cancer research agency. Focusing on cancer risk, IARC coordinates groups of scientists to identify potential carcinogenic hazards by examining literature regarding dietary and nondietary exposure to a particular substance. IARC’s conclusions indicate the strength of the evidence regarding a certain cancer hazard, not the risk posed by any given level of exposure to that hazard, and are stated in terms of one of four classifications:

  • Group 1: Carcinogenic to humans
  • Group 2A: Probably carcinogenic to humans
  • Group 2B: Possibly carcinogenic to humans
  • Group 3: Not classifiable as carcinogenic to humans

A group of 25 scientists from various countries reviewed publicly available literature regarding aspartame, including human and animal studies, and classified aspartame as being “possibly carcinogenic to humans” (Group 2B). The classification is based on several human studies reflecting a positive association between the consumption of artificially sweetened beverages and the risk of liver cancer. However, IARC described the studies as providing “limited evidence” and noted certain limitations, such as how the studies estimate exposure to aspartame, reverse causality concerns, bias, potential confounding socioeconomic or lifestyle factors, and others.

IARC also found that while there were some “positive findings in several studies available for genotoxicity,” there was “limited mechanistic evidence” that aspartame exhibits key characteristics of carcinogens.

The IARC’s findings were published in The Lancet Oncology and the complete evaluation and detailed assessment will be published in volume 134 of the IARC Monographs.

WHO Recommends No Change to Accepted Daily Intake in JECFA Finding

At the same time, a second WHO-affiliated scientific committee, the JECFA, analyzed the potential risks associated with exposure to aspartame.

The JECFA is an international scientific expert committee that is administered jointly by the Food and Agriculture Organization of the United Nations (FAO) and the WHO. Whereas IARC studies potential carcinogenic hazards, JECFA conducts risk assessments on those hazards and other substances to determine the probability that a particular type of harm (cancer and other diseases) will occur based on certain levels of dietary exposure. The JECFA states its conclusions in terms of “acceptable daily intake” (ADI), or the levels of the substance that are considered safe for human consumption.

The JECFA evaluated data from randomized controlled trials and epidemiological studies relating to aspartame and found that there was no convincing evidence that aspartame has adverse effects after ingestion. The JECFA noted that when ingested, aspartame is converted into chemicals that are identical to those absorbed after consuming common foods. The JECFA concluded that there was no reason to change the previously established ADI of 0–40 mg/kg body weight for aspartame. This amount is equivalent to 14 cans of diet soda per day.

Notably, the JECFA found that all of the human studies used by the IARC to support its “possibly carcinogenic” classification of aspartame had significant limitations in how they estimated exposure, and other contributing factors for cancer could not be ruled out, such as socioeconomic or lifestyle factors, or consumption of other dietary components.

FDA Rejects WHO Classification of Aspartame as ‘Possibly Carcinogenic’

Immediately after the WHO’s classification of aspartame was published, the FDA published its response, disagreeing with the IARC’s findings and supporting the JECFA’s conclusions.

The FDA analyzed the same literature that the IARC reviewed and identified significant shortcomings in those studies. The FDA also noted that aspartame is one of the most studied food additives and that it has reviewed more than 100 studies designed to identify aspartame’s possible toxic effects. FDA restated its position that aspartame is safe when used within recommended ADI levels of 50 mg/kg of body weight, which is higher than the JECFA’s ADI of 40 mg/kg of body weight.

The FDA has a long history of regulating aspartame as a food additive. In July 1974, it first approved the limited use of aspartame as a tabletop sweetener and in chewing gum, cold breakfast cereals, and dry bases for certain foods (for example, beverages, instant coffee and tea, gelatins, puddings and fillings, and dairy products and toppings). In July 1981, the FDA allowed the marketing of aspartame in dry foods. In July 1983, the FDA approved the use of aspartame in carbonated beverages and established an ADI of 50 mg/kg of body weight. The FDA continued to approve the use of aspartame for other products, including multivitamins, drugs (as an inactive ingredient), and various other products, culminating in its approval of aspartame as a general-purpose sweetener in June 1996.

In October 2014, the FDA denied two citizen petitions that asked the agency to revoke the authorizations for aspartame, citing the lack of substantive scientific evidence sufficient for the FDA to alter its conclusions about the safety of aspartame.

Action Items Companies Can Take to Limit Potential Exposure

As this is a developing issue, the repercussions of the WHO’s classification of aspartame as “possibly carcinogenic” are currently unknown. To the extent the classification leads to putative class action litigation, affected companies may have strong grounds to defeat any claims of purported consumer deception or any purported causal link to the claimed injury, in addition to defenses based on the FDA’s findings that aspartame is safe to ingest within the designated ADI.

We have nonetheless identified several action items that companies can take now in an effort to limit any potential exposure or liability.

Proper Labeling and Advertising Messages

Aspartame is commonly used as a low-calorie sweetener alternative to table sugar. Companies often tout the benefits of aspartame or products containing aspartame as “healthier” or “diet” alternatives to table sugar or sugar-based products. Companies should review their product labels and advertising and marketing messages for those products to ensure that they do not oversell the benefits of aspartame.

Adequate Insurance Coverage

Most companies have historic and current general liability policies that respond to and have a duty to defend claims seeking damages because of or for bodily injury as a result of exposure to or use of their products, such as products containing aspartame. These policies, which may include occurrence-based policies (which respond if the alleged bodily injury took place even in part during the policy period), claims-made policies, or Bermuda form policies, should be carefully analyzed to preserve rights to coverage and to determine both the amount of coverage available and the best approach to maximize insurance recoveries if underlying claims arise, taking into account deductibles or self-insured retentions, among other things.

Companies confronting potential liabilities arising out of products they manufactured or sold should confer with insurance advice and recovery counsel for advice on preserving their rights to coverage under, and understanding the potential responsiveness of, their insurance programs as to these potential liabilities.

Continue Monitoring the Legal Landscape

Companies should closely monitor the legal landscape to remain current with any lawsuits filed against similarly situated companies that use aspartame and to adjust policies and practices accordingly.


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